This invention relates to machine dishwashing compositions of relatively low phosphorus content in which superior performance is achieved using mixtures containing high-foaming nonionic surfactants in the absence of alkali metal silicates.
Synthetic detergents capable of performing a wide variety of household and industrial cleaning operations are known in the art and are formulated for optimized performance under the contemplated end use conditions. For example, machine dishwashing detergents are formulated for use in appliances in which a moving, high-velocity water spray is utilized for cleaning tableware and cooking utensils. The performance requirements for such a detergent differ substantially from the requirements for a laundry or hand-dishwashing detergent and include very low sudsing. effective rinsing to avoid residual deposits, thorough removal of food protein particles which can cause spot formation during drying, and sequestration of calcium and magnesium ions usually present in the water supply. Damage to the dishes being washed, such as etching of glassware, must also be avoided.
To meet the foregoing performance requirements, typical machine dishwashing detergents contain a relatively small amount of a nonionic surfactant, a small amount of a chlorine or oxygen-releasing bleach, a relatively large amount of a phosphate-type builder or sequestrant, and moderate to relatively large amounts of auxiliary sources of alkalinity, such as alkali metal carbonates and alkali metal silicates, which enhance the cleaning action and minimize corrosion. However, from the standpoint of environmental considerations, the presence of large amounts of phosphates or similar phosphorus-containing compounds in machine dishwashing detergents is very undesirable, and it is the objective of this invention to provide a practical powder dishwashing composition containing only about 10 to about 20 weight percent of phosphorus-containing compounds (instead of the 25 to 50 weight percent normally needed) while retaining superior washing action and without harming the dishes being washed.